1. Field of the Invention
The present invention relates to an optical pickup and an optical disc apparatus which are capable of recording and reproducing a plurality of types of optical discs such as CDs (Compact Discs), DVDs (Digital Versatile Discs) and BDs (Blu-ray Discs) and, more particularly, to optimum optical magnification of laser light for the kind of disc to be recorded or reproduced.
2. Description of Related Art
In recent years, CDs (Compact Discs: hereinafter “CD(s)”) and DVDs (Digital Versatile Discs: hereinafter “DVD (s)”) for recording and reproduction of image information and music information have become popular, and CD/DVD compatible pickups have been developed (refer to Patent Document 1 (Japanese Patent Laid-Open Publication No. Hei10-199026, Pages 3 and 4, FIG. 1)). In order to meet demands for further increases in recording density and storage capacity, a high-density optical disc such as a BD (Blu-ray Disc: hereinafter “BD”) using a blue-wavelength laser light of wavelength 407 nm have been introduced.
In such circumstances, optical disc apparatuses for recording and reproducing three types of discs such as CDs, DVDs and BDs have been developed and manufactured. Such an optical disc apparatus uses laser light beams of wavelengths 780 nm, 650 nm and 407 nm for recording and reproducing CDs, DVDs and BDs. In this structure, if an optical system which includes an objective lens for focusing laser light onto a disc and receiving light reflected from the disc can be shared by the three types of laser light beams, the optical system can be made simple, whereby a further decrease in size and weight of optical pickups can be realized.